What is the oldest written source in this country that mentions this right?
Mauritania
Mauritania’s 1961 Constitution drew from the French Declaration of the Rights of Man and included press freedom protections (Handloff 1987, p. 126).
Today, however, Mauritania’s 1991 Constitution contains no explicit protections on press freedom (Constitute Project, “Mauritania’s Constitution of 1991 with Amendments through 2012”).